The present invention is concerned with a medicinal feed for the systemic treatment of parasites in fish.
The care, breeding, and maintenance of fresh water and marine fish in hobby aquaria, in ponds and, to an even greater extent, in intensive maintenance installations of fish farming and aquaculture, are threatened by parasitic diseases which can endanger the fish and result in considerable financial losses. The following organisms pathological to fish occur especially frequently: dinoflagellates: Oodinium pillularis (fresh water) and Oodinium ocellatum (seawater); flagellates: Costia necatrix and Hexamita symphysodonis; ciliates: Ichthyophthirius multifilis (fresh water); monogenes: skin and gill flukes, for example Gyrodactylus and Dactylogyrus.
The treatment of ectoparasitoses, i.e., of diseases caused by parasites which live in or on the outer skin of fish, today occurs exclusively by the so-called bath therapy in which antiparasitic material is added to the maintenance water in appropriate biocidal concentrations.
Frequently, only the free-swimming parasitic stages, the so-called swarms, are thereby damaged but not the stages sitting securely in the skin or under the outer skin.
Consequently, the total treatment is based on the killing off of the swarms. There is no prevention of a new infection or reinfection or no effect on the immune system of the fish which additionally or exclusively combats the parasitic pathogenic stages.
According to the prevailing expert opinion, ectoparasitic diseases can only be treated externally and not be means of systemically administered curative agents, for example, medicinal feeds.
Endoparasitic diseases, for example, parasites of the gut, can be treated successfully almost exclusively by systemically administered curative agents, for example, medicinal feeds, such as are described in the literature (see N. Herwig, "Handbook of Drugs and Chemicals used in the Treatment of Fish Diseases" , pp 128 and 136, pub. Charles C. Thomas, Springfield, Ill., U.S.A.; E. Amlacher, "Taschenbuch der Fischkrankheiten", pub. Gustav Fischer Verlag, Stuttgart, 1981; L. Zemer, Das Aquarium, 220, 515/1987).
The bath therapy of ectoparasitic diseases of fish (fancy fish and useful fish) is frequently carried out with the use of biocidally or antiseptically acting dyestuffs, for example, of the triphenylmethane and acridine group of derivatives. These compounds include, for example, N-[4-[[4-(diethylamino)-phenyl]-phenylmethylene]-2,5-cyclohexadien-1-ylide ne]-N-ethyl -ethanaminium sulphate (brilliant green); N-[4-[[4-(dimethylamino) -phenyl]-phenylmethylene]-2,5-cyclo-hexadien-1-ylidene]-N-methyl-methanami nium chloride and oxalate (malachite green); N-[4-[bis-[4-(dimethylamino)-phenyl]methylene]-2,5-cyclohexadien-1-ylidene ]-N-methylmethanaminium chloride (gentian violet); 3,6-diamino-10-methylacridinium chloride mixed with 3,6-dimainoacridine (acriflavine); 9-aminoacridine; and 2-ethoxy-6,9-diaminoacridinium lactate monohydrate (Rivanol) .
In addition, active antiparasitic materials from other classes of chemical compounds are also used, for example, quinoline derivatives such as quinine; quaternary ammonium salts; silver and copper salts; metal colloids, nitrofurans, for example, nifurpirinol; and nitrothiazoles, for example, 2-amino-5-nitro-thiazole.
However, the bath therapy with these antiparasitic active materials involves several disadvantages. Parasites in or under the outer skin of the fish are mostly not affected. Since frequently the whole of the maintenance water (aquarium, pond, or intensive breeding installation) is treated, in addition, a very large use of active material is necessary.
Furthermore, the active material concentration is very uncertain since, during the treatment, due to decomposition processes (chemical, biological, and photochemical) and adsorption on surfaces, losses of active material occur which cannot be previously calculated. Since, to a large extent, the materials used are dyestuffs, the intensive coloration of the water and the tendency of the bath solution to color various materials is also disturbing. Since the whole of the maintenance system is therapeutically treated, the presence of the biocidally active materials leads to undesirable and, under certain circumstances, even harmful side effects, for example, damage to other important water organisms, such as aquatic plants and planktonic organisms and damage of the biological flora in filter systems and thus a negative influence on the biological breakdown capacity. The above-mentioned therapeutically active compounds also have a strong fish toxicity and especially gill toxicity so that the safety of the treatment is limited.